Min Reaction Time Research Articles

Biodiesel production from food waste using insitu transesterification method

The present study deals with the management of waste food with the different approaches in which waste food is used to extract biodiesel and based on this, the work deals with the optimization of process parameters for biodiesel synthesis from food waste with insitu transesterification reaction. The main process parameters selected arecatalyst (KOH) concentration (0.0–2.0% w/w), methanol/food waste ratio (v/v) (50–100%), and reaction duration (60–180 min). The temperature of the reaction was kept constant at 50 °C. The reaction temperature was taken low so that in future this low temperature can be obtained from solar energy or waste process heat. The yield of biodiesel, chosen as the output, has been evaluated using Box-Behnken Design in the Response Surface Methodology. A biodiesel yield of 96.62% has been obtained with methanol/food waste proportion of 98.33% and a catalyst amount of 1.35% (w/w) in 107.06 min of reaction time at 50 °C.

Electrochemical treatment of wastewater containing urea-formaldehyde and melamine-formaldehyde

The wastewater containing urea-formaldehyde (UF) and melamine-formaldehyde (MF) from the medium-density fiberboard (MDF) lamination factory disposed into the waterbodies adversely affects human health and aquatic life. Therefore, its treatment before discharge is necessary. Researchers have used various techniques to treat this type of wastewater in the past, but none have tried electrochemical (EC). However, EC can potentially remove pollutants such as chemical oxygen demand (COD), total organic carbon (TOC), formaldehyde (FA), total nitrogen (TN), nitrogen nitrate (NO3–N), and other hydrocarbons. Hence, this study uses the EC technique to treat wastewater containing UF and MF with aluminium electrodes. The experiments were run in batch mode with a 250 mL working volume in a 500 mL Pyrex glass beaker using a variable DC power supply (0–30 V and 0–5 A). The impacts of various parameters, including reaction time (RT) 30–240 min, current density (CD) 8.66–51.94 mA/cm2, inter-electrode distance (IED) 1–2 cm, and mixing speed in the range of 60–120 rpm were examined to achieve the best pollutant removals. The best removal percentage was reached at the optimized conditions of 150 min RT, 43.28 mA/cm2 CD, 1.5 cm IED, and 80 rpm: 81.1% TOC, 61.5% COD, 76.7% TN, 28.3% NO3–N, and 55.2% FA. During the EC process, electrodes and energy consumption were estimated at around 2.367 (g/L) and 0.18 (kWh/L), respectively. A kinetic analysis was also carried out to determine the pollutant's removal trend. This study concluded that the pseudo-first-order kinetic model was the best fit for removing TOC and FA with regression coefficients of 0.96 and 0.83, respectively.

Utilizing an ultra-sonication process to optimize a two-step biodiesel production from Karanja oil.

Currently, biodiesel is produced from non-edible oils, which have various poisonous and un-saponifiable components; therefore, it is harmful and unfit for humans. Biodiesel replaces petro-diesel fuel, which can be used as additives or substitutes for diesel engines. The novelty of the present study is to optimize the process parameters of a two-step (esterification and transesterification) process for biodiesel production using high free fatty acid (FFA) containing Karanja oil (Pongamia pinnata oil), with the ultrasound (US) process intensification (PI) technique, which is carried out for the first time. In the first step, a reduction in the initial FFA concentration of 11.06% was achieved through optimization of the esterification process using response surface methodology (RSM)-supported central composite design (CCD) method in which methanol:oil molar ratio of 6:1 and 60°C reaction temperature kept as fixed parameter, whereas H2SO4 catalyst loading (0.5-1.5w/w%) and reaction time (15-45min.) were varied. The FFA value is reduced to 1.56% under the optimal condition (32.8min reaction time and 1.14 w/w% of catalyst loading). The second step of optimization of the transesterification of esterified oil was performed by applying RSM supported Box-Behnken design (BBD) method with varying independent parameter ranges such as the molar ratio (A), CH3OK catalyst loading (B), and reaction time (C) with the range of 6:1-9:1 (methanol: oil), 0.5-1.5 w/w%, and 10-30min., respectively. A biodiesel yield of 98.16% was obtained under optimal conditions of a molar ratio of 7.6:1, catalyst loading of 0.98 w/w%, a reaction time of 20.6min., and a reaction temperature of 60°C (constant). Superior optimization results were observed than the conventional stirring method. The biodiesel's estimated characteristics were discovered to be within ASTM criteria and suitable for blending with diesel fuel.

Box–Behnken optimization of biodiesel production using trisodium phosphate catalyst from monazite ore processes

AbstractTrisodium phosphate (TSP) is a non‐toxic waste obtained from alkaline cracking as part of the processing of monazite ore. After simple purification, TSP can be utilized in many applications; however, it is used as a catalyst in this study. It is characterized using Thermogravimetric analysis , X‐ray diffraction analysis, Brunauer‐Emmett‐Teller, and Temperature‐programmed desorption of carbon dioxide and optimized in the transesterification reaction. After recrystallization and calcination at 350 °C for 0.5 h, the form of the TSP was tetragonal, with a 2.61 m2/g surface area and 537.4 x 10‐6 mol/g basic sites. Trisodium phosphate can therefore be utilized effectively as a solid base catalyst for the transesterification of palm oil. Three biodiesel production parameters were investigated: the methanol to oil molar ratio (6:1–24:1), catalyst concentration (1–10%), and reaction time (30 to 240 min). The experiments were designed using the Box–Behnken response surface method. As a result, the optimum conditions for biodiesel production are a 22:1 methanol to oil molar ratio, 4% catalyst concentration, and 200 min reaction time. The optimal fatty acid methyl ester (FAME) content is 99.79%, with an error between actual and predicted FAME of 0.21%. © 2023 Society of Industrial Chemistry and John Wiley & Sons Ltd.

River snail shell as a highly effective renewable heterogeneous base catalyst for the production of biodiesel

The biodiesel manufacturing process favors heterogeneous catalysts over homogeneous catalysts. The main drawbacks of using homogeneous catalysts are their non-renewable nature, separation, and washing, which can be avoided by using heterogeneous catalysts. This research looks into the shell of a river snail (Viviparidae) that has been improved with modified activated carbon (MAC) as a heterogeneous solid base catalyst for palm oil transesterification. The waste shell was repeatedly washed to remove any organic impurities attached to it and then dried in an oven. It was calcined in an air atmosphere for 2 h at a high temperature of 900 °C. The calcined sample (calcium oxide: CaO) was powdered and mixed with MAC. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and the Brunauer-Emmet-Teller (BET) method were used to characterize the CaO/MAC (mass fraction 3:1) catalyst. In order to optimize the reaction conditions for biodiesel production, operating parameters such as methanol to oil mole ratio, catalyst amount, reaction time, and microwave electrical power were investigated. As a result, the best reaction parameters were discovered to be 12:1 methanol to oil mole ratio, 2.5 wt.% CaO/MAC based on oil weight, 4 min of reaction time, and 600 W microwave electrical power. After being reused five times, the biodiesel yield could still reach 90%, indicating that the novel catalyst had good stability and recyclability. The biodiesel fuel properties obtained in this study were compared to the international biodiesel standards ASTM D6751 and EN14214. River snail shell can be thought of as a nature-based benign and resourceful material for biodiesel production, opening up a new path for fuel sustainability.

Conversion and rate behavior of brown macroalgae in pyrolysis: Detailed effects of operating parameters

Non-catalytic pyrolysis of brown macroalgae (Padina sp.) was studied in a batch reactor at temperature ranges of 400–600 °C and 10–90 min reaction times on the product distribution and conversion rate behavior. The highest pyro-oil and pyro-gas yields were obtained at 600 °C, which reached 67 wt% and 27 wt%, respectively, when the reaction times were prolonged (30–90 min). In addition, the high reaction temperature resulted in more generations of heavy tar and a considerable enhancement in aromatization degree. N-aromatic groups and phenol were observed from pyro-oil at 500 °C and 600 °C, respectively. Tar yield increased with reaction temperature, reflecting an order of reaction greater than one for tar production. The rate constant of tar formation was found to be 0.0013/s at 400 °C; 0.0023/s at 500 °C; and 0.0033/s at 600 °C, respectively, with the reaction order being higher than one (1.25). These findings highlighted that the proposed model could be used to accurately predict the pyrolysis process's behavior.

The Application of Clinoptilolite as the Green Catalyst in the Solvent-Free Oxidation of α-Pinene with Oxygen

In this work, we present the catalytic application of the naturally occurring zeolite, clinoptilolite, in the oxidation of α-pinene, a natural terpene compound. Clinoptilolites with different average particle sizes, designated as (in μm) clin_1 (20), clin_2 (50), clin_3 (200), and clin_4 (500–1000), were used as the green catalysts in the solvent-free oxidation of α-pinene with oxygen. Prior to their application in catalytic tests, the catalysts were characterized by the following methods: nitrogen sorption at 77 K, EDXRF, XRD, SEM, UV-Vis, and FTIR. The effects of the temperature, amount of the catalyst, and reaction time on the product’s selectivity and α-pinene conversion were determined. At the optimal conditions (a temperature of 100 °C, catalyst content (clin_4) in the reaction mixture of 0.05 wt%, and 210 min reaction time), the following compounds were obtained as the main products: α-pinene oxide (selectivity 29 mol%), verbenol (selectivity 17 mol%), and verbenone (selectivity 13 mol%). The conversion of α-pinene under these conditions amounted to 35 mol%. Additionally, the kinetic modeling of α-pinene oxidation over the most active catalyst (clin_4) was performed. The proposed method of oxidation is environmentally safe because it does not require the separation of products from the solvent. In addition, this method allows for managing the biomass in the form of turpentine, which is the main source of α-pinene. The catalytic application of clinoptilolite in the oxidation of α-pinene has not yet been reported in the literature.

Enhanced photo-degradation of diclofenac using a new and effective composite (O-g-C3N4/TiO2/α-Fe2O3): Degradation pathway, toxicity evaluation and application for real matrix

Removing persistent pharmaceutical compounds from wastewater, such as sodium diclofenac (DCF), has become challenging in recent years. This study aimed to introduce a simple and navel method for synthesizing a new O-g-C3N4/TiO2/α-Fe2O3 (OCNTF) photocatalyst and examine its performance in DCF degradation from aqueous solutions. During 60 min reaction time, a complete of 10 mg/L DCF was removed by a 1.0 g/L catalyst in a 40 ml DCF solution at pH 6.75 while 41.75% of total organic carbon (TOC) was removed under the same conditions. In the same situation, the photocatalytic efficiency for natural wastewater was 97.36% in 3 h. CO32- and HPO42- were the most to cause diclofenac degradation inhibited.A Mott-Schottky analysis, measurements of band edge location, and active species trapping were used to predict the mechanism of the S Scheme. •OH played an essential role in the photo-degradation of DCF by OCNTF and displayed excellent photocatalytic reactivity for DCF over 5 cycles. LC-MS was used to identify various intermediates formed during photocatalysis, and degradation pathways were investigated. In addition, the ECOSAR program predicted that UVA/OCNTF could be classified as an eco-friendly process. It has been shown that this catalyst can be considered for eliminating emerging pollutants from water environment.

One factor at a time and two-factor optimization of transesterification parameters through central composite design (CCD) for the conversion of used peanut oil (UPNO) to biodiesel

This present investigation has optimized the acid and base catalysed transesterification process parameters to enhance the conversion of used peanut oil (UPNO) into biodiesel through a central composite design. Of the different acid and alkali catalysts tested, KOH and H2SO4 were found to be efficient catalysts, which yielded 94.2% UPNO biodiesel. For one factor at a time approach, four reaction parameters such as catalyst dose, reaction time, methanol volume, reaction temperature, and speed of mixing were chosen and a catalyst dose of 1 g and reaction time of 60 min was found to be an independent influential factor to enhance UPNO yield. Therefore, KOH/ H2SO4 catalyst concentration and reaction time were selected to ascertain their synergistic effect on the UPNO biodiesel production through central composite design (CCD). Two factorial CCD design unveils that 1.5 g catalyst (acid and alkali) and 90 min reaction time are the optimal conditions along with 70 °C reaction temperature, 6 mL methanol volume, and 50 rpm stirring speed for high UPNO biodiesel yield of 95.9%. In addition, the fatty acid profile of UPNO biodiesel contains oleic acid and linoleic acid as dominant fatty acids in the range of 55–56 % and 25–27%, respectively in KOH and H2SO4 catalysis. Further, MUFAs, PUFAs, and SFAs levels of UPNO biodiesel produced by H2SO4 catalyst were 55.44, 25.66 and 16.43 %, respectively while they were 56.12, 26.32 and 14.53%, respectively for KOH catalysis. Based on the results of high UPNO biodiesel and MUFA levels, it is contemplated that UPNO biodiesel could be a promising alternative fuel from a commercialization perspective.

Humic Acid Removal by Electrocoagulation Process from Natural Aqueous Environments

Humic acid results in formation of highly toxic and carcinogenic byproducts during the disinfection process of water by chlorine. In this study, removal of industrial humic acid from artificial and natural aqueous media is investigated using electrocoagulation process. To reach the goal, first, humic acid-contaminated water samples with concentrations of 20 mg/L were prepared in a reactor with the effective volume of 1 L, equipped with iron electrodes. Then, the effects of pH (2 up to 9) and electric potential of 30 V was studied by measurement of UV radiation absorption and total organic materials methods, on the coagulation process in removal of humic acid within 80 min. According to the results of this study, the best efficiency in removal of humic acid was obtained as 92.69 by electrochemical process when the parameters were adjusted as; potential difference of 50 V, 80 min reaction time, pH 5, and electric conductivity of 3000 I¼S/cm. In the optimum condition, the efficiency of humic acid removal from natural water was obtained as 68.8. The results indicated that, the electrochemical process equipped with iron electrodes could remove humic acid from aqueous media, efficiently. © 2018 The Authors.

PH-responsive, stable, and biocompatible functional nanogels based on chitosan (CS)/poly methacrylic acid (PMAA) polymers: Synthesis and characterization

Nanogels are presently the subject of a great deal of research worldwide due to their intriguing properties, such as biodegradability, biocompatibility, non-toxicity, and small size. Nanogels have great potential in biomedical and pharmaceutical fields, particularly drug delivery systems, owing to their high loading capacity, control, and targeted drug delivery. The current study aims to synthesize pH-responsive, biocompatible, chemically and physically crosslinked chitosan/polymethacrylic acid (CS/PMAA) based nanogels. FTIR study confirms the respective functional groups of CS, PMAA, and nanogels. Moreover, SEM and DLS analyses affirmed the formation of nanogels, which are submicron in size (> 200 nm and < 200 nm for 30 and 60 min reaction times, respectively). The prepared nanogels have manifested excellent stability (+ 31.66 mV and −33.12 mV, for cationic and anionic nanogels, respectively) under zeta potential measurements. The nanogels owned good thermal stability as characterized by DSC, and XRD results depict the semicrystalline structure. Cytotoxicity of prepared nanogels against PBMC cells was evaluated after 4hrs of exposure, and the cell viability of > 80% was observed for all the concentrations (1–100 μg/mL) of nanogels. However, high concentrations demonstrated viability loss due to the toxicity effect of NH3+ ions binding to negatively charged cell membranes. The experimental results from this study offer counseling for designing and developing CS-based nanogels for the diversity of applications in the biomedical and pharmaceutical industries.

Research on microwave hydrothermal alkaline leaching defluorination of spent cathode carbon from aluminum electrolysis

Soluble fluoride present in spent cathode carbon (SCC) is a serious concern for both the environment and human health. To address this issue, the microwave hydrothermal alkaline leaching (MHAL) was used to removed the soluble fluoride from SCC. The structural characteristics and elemental distribution of SCC before and after MHAL treatment were analyzed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). The effect of the primary parameters, i.e., temperature, time, and alkali concentration in the MHAL process, on the soluble fluoride removal rate was assessed using the Box-Behnken design (BBD) in response surface methodology (RSM), and subsequently optimized. The optimization results illustrate that the soluble fluoride removal rate of SCC could reach up to 98.06% under the optimum reaction conditions of 80 °C, 1.16 mol/L alkali concentration, and 8.4 min of reaction time. Under this condition, the experimental data showed that the average soluble fluoride removal rate was 97.11% and were in good agreement with the model predicted values. Furthermore, the MHAL process reduced the treatment process time by 99.4% and increased the soluble fluoride removal rate by 5.8% compared to the traditional hydrothermal treatment process. The MHAL process ensures rapid and efficient hazardous treatment of SCC while minimizing environmental pollution.

Enzymatic degradation of azo dyes methylene blue and congo red with peroxidase purified from cauliflower using affinity chromatography technique: Kinetic study, optimization and metal binding activity

The effective results of the enzymatic decolorization of industrial azo dyes found in wastewater, which cause serious health and environmental problems, with peroxidases have recently increased the interest in these enzyme sources. Redox-mediated decolorization of Methylene Blue and Congo Red azo dyes with cauliflower (Brassica oleracea var. botrytis L.) peroxidase (CPOD) purified in one step using 4-amino 3-bromo 2-methyl benzohydrazide molecule was investigated for the first time. The inhibition effect of this molecule, which is used as a ligand in affinity chromatography, on the CPOD enzyme was investigated. The Ki and IC50 values for this enzyme were calculated as 0.113 ± 0.012mM and 0.196 ± 0.011mM, respectively. With the affinity gel obtained by binding to the Sepharose-4B-l-tyrosine matrix of this molecule, which shows a reversible inhibition effect, the purification values of CPOD enzyme were determined as 562-fold with a specific activity of 50,250 Umg-1. The purity of the enzyme was checked by the SDS-PAGE technique and its molecular weight was determined. A single band at 44kDa was observed for the CPOD enzyme. In dye decolorization studies, the effects of dye, enzyme, and hydrogen peroxide concentrations as well as time, pH, and temperature were investigated. The profiles of the optimum conditions for both dyes were similar, and the percentages of decolorization of Methylene Blue and Congo Red under these conditions were 89% and 83%, respectively, at the end of the 40min reaction time. Again, when examining the effect of metal ions on enzyme activity, it was found that there was no significant negative change in CPOD.

Experimental and kinetic studies of the advantages of coke accumulation over Beta and Mordenite catalysts according to the pore mouth catalysis hypothesis

Coke formation inside heterogeneous reactors is an important industrial problem that leads to reduced catalyst efficiency. However, this study aims to prove the benefits of coke build-up in improving catalyst performance. The formation and decomposition of coke on six different zeolite structures was studied. The dissociation kinetic model of the spent catalysts during the toluene alkylation with 1-heptene inside a stainless-steel autoclave reactor at different temperatures was carried out. Various techniques (XRD, XRF, TPO, CHNS and TGA-DTG) were used. It was found that the conversion and selectivity of the desired product were higher on the parent H-mordenite and the dealuminated H-beta catalysts with conversions of 85.3% and 84.67%, respectively, at a 360 min reaction time. This was attributed to the reduction of the ratio of hard:soft coke. It is confirmed that the decomposition activation energies of hard coke, 140.1–202.6 kJ/mol, are much higher energies than those of soft coke, 89.9–118.7 kJ/mol. It is also noted that the hypothesis of pore mouth catalysis is dominated by non-polyaromatic coke on the surface of the H-beta catalysts, while the hypothesis is dominated by polyaromatic coke on the surface of the H-mordenite catalysts.

Phosphorus recovery from aqueous product of hydrothermal carbonization of cow manure

The work studies the recovery of nutrients (phosphorus and nitrogen) from the process water of acid-assisted hydrothermal carbonization (HTC) of cow manure. Three organic acids (formic acid, oxalic acid, and citric acid) and sulfuric acid were evaluated as additives in HTC. Using 0.3 M sulfuric acid, more than 99% of phosphorus and 15.6% of nitrogen from manure are extracted and dissolved during HTC at 170 °C with 10 min reaction time in a batch reactor. Nutrients (mainly phosphorus) were recovered through precipitation from process water by raising the ionic strength of the solution by addition of salts of magnesium and ammonia, and by raising the pH to 9.5. Subsequently, phosphorus-rich solids were recovered containing almost all (greater than 95%) of the dissolved phosphorus in the sulfuric and formic acid assisted runs. Morphology and qualitative chemical analysis of the precipitates were determined. It is shown by XRD that the precipitate formed from process water generated by HTC with oxalic acid is crystalline, although the diffraction pattern could not be matched with any expected substance.

Development of a continuous silica treatment strategy for metal extraction processes in operating geothermal plants

The extraction of rare metals like lithium (Li) from geothermal fluids is a promising alternative to conventional mining. Membrane distillation (MD) could support energy-efficient fluid treatment enabling further freshwater production. For the operation of geothermal plants and MD uncontrolled precipitation of silica (Si) represents a major hurdle. Herein, we demonstrate the transfer of a Si treatment from lab to field demonstrator scale, tested under conditions of an operating geothermal power plant.For the treatment, lime precipitation was chosen showing good Si reduction rates using artificial fluids. The high alkaline conditions of this process (pH > 10) in combination with the high salinities of the geothermal brines (TDS > 100 g/L) are transferred into real geothermal environment with a newly developed numerical design calculation. The resulting demonstrator consists of three major process steps - 1) Si-reduction, 2) liquid/solid separation, and 3) post-concentration using MD. The Si treatment efficiently reduced 98 % of Si in <5 min reaction time, without influencing the lithium concentration negatively. The MD resulted in Li concentrations of ∼500 mg/L while producing fresh water. Beyond the approval of the concept, neuralgic points for improvement were identified expanding fundamental knowledge about the material use of geothermal fluids.

Research on the distribution of S species in the pressure oxidation leaching process of SrS solution

Strontium compounds apply extensively in a variety of domains. Commonly, strontium compounds are made by carbonization of SrS solution. H2S is readily generated in this process. To avoid H2S byproducing, a novel strategy for the pressure oxidation leaching process of SrS solution was used. The overoxidation of sulfides was restrained, and a higher separation efficiency of Sr and S was obtained, which was beneficial for synthesizing other strontium compounds. The effects of the oxidation pH environment, reaction temperature, initial total sulfide concentration and reaction time on the conversion ratio of S species were investigated. The results showed that S0 was preferably generated in a near-neutral, low-temperature and low initial total sulfide concentration oxidation environment. The optimum oxidation conditions were summarized experimentally: 48 mL/L HCl (pH = 7.11), 25 °C reaction temperature, 8.2 g/L initial total sulfide concentration and 60 min reaction time. The optimum conversion ratios were obtained under optimum oxidation conditions as follows: χsulfide 2.3%, χH2S 0.5%, χS0 81.5%, χinter 10.0% and χS - Sr 5.7%. SrCl2 crystal was recovered finally from the leachate. At last, the pressure oxidation mechanism of SrS was discussed.

Microwave-assisted biodiesel production using –SO3H functionalized heterogeneous catalyst derived from a lignin-rich biomass

The synthesis of biodiesel from renewable resources has immense potential as a sustainable and cost-effective energy alternative. In this work, a reusable –SO3H functionalized heterogeneous catalyst that has a total acid density of 2.06 mmol/g was prepared from walnut (Juglans regia) shell powder by low-temperature hydrothermal carbonization (WNS-SO3H). Walnut shell (WNS) contains more lignin (50.3%), which shows great resistance toward moisture. The prepared catalyst was employed for the effective conversion of oleic acid to methyl oleate by a microwave-assisted esterification reaction. The EDS analysis revealed the significant presence of sulfur (4.76 wt%), oxygen (51.24 wt%), and carbon (44 wt%) content. The results of the XPS analysis confirm the bonding of C–S, C–C, C=C, C–O, and C=O. Meanwhile, the presence of –SO3H (the responsible factor for the esterification of oleic acid) was confirmed by FTIR analysis. Under the optimized conditions (9 wt% catalyst loading, 1:16 oleic acid to methanol molar ratio, 60 min reaction time, and 85 °C temperature), the conversion of oleic acid to biodiesel was found to be 99.01 ± 0.3%. The obtained methyl oleate was characterized by employing 13C and 1H nuclear magnetic spectroscopy. The conversion yield and chemical composition of methyl oleate were confirmed by gas chromatography analysis. In conclusion, it can be a sustainable catalyst because the catalyst preparation controls the agro-waste, a great conversion is achieved due to the high lignin content, and the catalyst was reusable for five effective reaction cycles.

Degradation of tetracycline by activated peroxodisulfate using a sulfur-modified iron-based material.

The activation of persulfate by an iron-based catalyst presents a promising approach for the degradation of antibiotics; however, the activation efficiency remains a challenge. Herein, a sulfur-modified iron-based catalyst (S-Fe) by co-precipitation of sodium thiosulfate and ferrous sulfate in a molar ratio of 1:2 was prepared and the efficacy of the S-Fe/PDS system for the removal of tetracycline (TCH) was studied, where a higher removal efficiency was observed compared to the Fe/PDS system. Moreover, the effects of TCH concentration, PDS concentration, initial pH, and catalyst dosage on TCH removal were evaluated, and the highest efficiency was about 92.6% within a 30 min reaction time using a catalyst dosage of 1.0 g/L, a PDS dosage of 2.0 g/L, and a solution pH value of 7. The products and degradation pathways of TCH were analyzed by LC-MS. The free-radical-quenching experiments revealed that both SO4- • and •OH radicals contributed to the degradation of TCH in the S-Fe/PDS system, with the former playing a more significant role. The S-Fe catalyst also showed good stability and reusability for the removal of organic pollutants. Our findings suggest that the modification of an iron-based catalyst offers an effective approach to activate persulfate for removal of tetracycline antibiotics.

Large Scale Cultivation and Pretreatment Optimization of Freshwater Microalgae Biomass for Bioethanol Production by Yeast Fermentation

The rapid depletion of the world’s fossil fuel reserves and global warming issues have promoted the search for sustainable alternative energy resources. In the present investigation, large-scale cultivation of naturally isolated freshwater microalgae Asterarcys quadricellulare strain was carried out using tertiary treated municipal wastewater as a growth medium in an open HRP pond for bioethanol production. A total of 12.091 kg of dry biomass was obtained at the end of the study. The lipid extracted carbohydrate rich spent microalgae biomass was converted to bioethanol by ethanolic fermentation. The biomass was first pre-treated with different concentrations of H2SO4 and HCL hydrolysis with different temperatures and reaction times. The biomass treated with a 2.0% concentration of H2SO4, showed maximum yields of glucose 308.38 mg.g-1 at 100°C with 180 min reaction time. The hydrolysates derived from the hydrolysis of microalgae biomass were used as a substrate for fermentation by using S. cerevisiae. The obtained bioethanol was analyzed using HPLC and the purity of ethanol was 90%.